The invention relates to a loudspeaker diaphragm provided with a rear load, the loudspeaker diaphragm exhibiting a point symmetry with respect to the center point of the loudspeaker diaphragm and/or an axial symmetry with respect to an axis extending through the center point of the loudspeaker diaphragm. The loudspeaker diaphragm and its rear load form the surface of a volume with openings being introduced into the surface of this volume. The openings introduced into the loudspeaker diaphragm and the center points of the openings exhibit a point symmetry with respect to the center point of the loudspeaker diaphragm and/or an axial symmetry with respect to an axis extending through the center point of the loudspeaker diaphragm.
From German (Auslegeschrift) published Examined Application 1,109,736, a generic loudspeaker diaphragm is already known which is attached to a part of a moving coil system and forms a volume with a rear wall. In this arrangement, the loudspeaker diaphragm is provided with holes which exhibit a point and axial symmetry with respect to the center point. These holes can have a circular shape in this arrangement.
In addition, a loudspeaker diaphragm is known from German Patent Document DE 22 36 374 A1 which is connected to a moving coil system in a magnet arrangement for the purpose of generating sound waves. In this arrangement, the loudspeaker diaphragm forms the surface of a volume with the magnet arrangement. Furthermore it is known from German Patent Document DE 22 36 374 A1, to introduce air gaps into the magnet arrangement in order to reduce the volume of the air to be compressed by the loudspeaker diaphragm. This is achieved, by the air being urged out of the volume through the air gaps of the magnet arrangement during the phase when the loudspeaker diaphragm is moving towards the magnet arrangement. When the loudspeaker membrane is moving away from the magnet arrangement again, the air follows into the volume through these air gaps.
It is an object of the invention to minimize disturbing effects on the vibration characteristic of a loudspeaker diaphragm that are due to air to be compressed during the process of movement of the loudspeaker diaphragm, and in so doing to improve the vibration characteristic of the loudspeaker diaphragm at the same time.
In a loudspeaker diaphragm of the above-noted type, this object is achieved, according to a preferred embodiment, by means of an arrangement wherein a further loudspeaker diaphragm is attached behind the loudspeaker diaphragm,
wherein the further loudspeaker diaphragm is point-symmetric with respect to the center point of the loudspeaker with further diaphragm and/or axially symmetric with respect to an axis extending to the center point of the loudspeaker diaphragm, this center point of the further loudspeaker diaphragm being located on a line which passes through the center point of the further loudspeaker diaphragm, this line forming a right angle with the loudspeaker diaphragm,
wherein the further loudspeaker diaphragm is connected force locked in the area of the center point to the same part as the moving coil system as the further loudspeaker diaphragm, and the further loudspeaker diaphragm is coupled at its outer circumference to the loudspeaker diaphragm, the outer circumference of the further loudspeaker diaphragm being located with the area of the loudspeaker diaphragm which is defined by the inner edge of the outer are,
wherein the openings of the loudspeaker diaphragm are introduced in the part of the area of the loudspeaker diaphragm which forms a volume with the further loudspeaker diaphragm, and
wherein the loudspeaker diaphragm and the further loudspeaker diaphragm are attached to the moving coil system with a particular spacing.
Further advantages of the invention compared with the known prior art consist in the fact that the mass of the loudspeaker diaphragm to be moved during the vibration process is reduced, which leads to an improved response to the loudspeaker, particularly at high frequencies. In addition, the vibration characteristic of the loudspeaker diaphragm at high frequencies is improved.
In wide-band loudspeakers, one aim is to concentrate the area vibrating at high frequencies to the center of the loudspeaker diaphragm by means of constructional measures. Due to its dimensions, the vibration of the overall loudspeaker diaphragm leads to interference phenonema at high frequencies which result in a distinct directional characteristic of the radiation at these high frequencies. On the other hand, the loudspeaker diaphragm must have a certain minimum size in order to be able to transmit low frequencies correctly.
In addition, flat loudspeakers, in particular, have the problem of distortions due to the air located behind the loudspeaker diaphragm, which must be compressed by the loudspeaker diaphragm during its movement. When during this process the loudspeaker diaphragm is moving in one direction which leads to a compression of the air located behind the loudspeaker diaphragm, the increasing pressure of the compressed air leads to a restoring force on the loudspeaker diaphragm. When the loudspeaker diaphragm is moving in a direction which leads to an enlargement of the volume in which the air is located, this enlargement of the volume likewise causes a restoring force. These two effects described occur predominantly with high amplitudes of the vibration of the loudspeaker diaphragm.
In the present invention, the volume given by the magnet arrangement and the loudspeaker diaphragm is to be opened, particularly in the case of a flat loudspeaker, in such a manner that during the movement of the loudspeaker diaphragm, the air can be displaced out of the volume or drawn into this volume through openings in the surface of the volume. According to the invention, this is achieved when openings are introduced into the loudspeaker diaphragm. During the process of movement of the loudspeaker diaphragm, air can flow through these openings into the volume or out of this volume. Further more, the introduction of openings into the loudspeaker diaphragm results in a reduction of the mass of the loudspeaker diaphragm to which movement must be imparted during a vibration. As a result, the loudspeaker diaphragm responds more quickly to high frequencies. In addition, a suitable dimensioning and arrangement of the openings makes it possible to achieve that at high frequencies in particular in the inner part of the loudspeaker diaphragm comes to vibrate.
In this arrangement, the openings in the loudspeaker diaphragm are preferably circles and, in the case of a point-symmetrical shape of the loudspeaker diaphragm with respect to the center point of the loudspeaker diaphragm and/or in the case of with an axially symmetrical shape of the loudspeaker diaphragm with respect to an axis extending through the center point of the loudspeaker diaphragm and/or an axially symmetrical arrangement with respect to an axis extending through the center point of the loudspeaker diaphragm.
It is also contemplated according to certain embodiments to attach a second smaller loudspeaker diaphragm to the first one. As a result, the inner area of the first loudspeaker diaphragm is stabilized and thus only the inner area of the first loudspeaker diaphragm vibrates, particularly at high frequencies. In an advantageous embodiment, the loudspeaker diaphragm exhibits a non-stiffened outer area so that an elastic connection to the housing wall is given through this outer area of the loudspeaker diaphragm. In this case, the second loudspeaker diaphragm is attached in the part of the area of the first loudspeaker diaphragm which is limited by the inner edge of the outer area of the first loudspeaker diaphragm.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.